1. Field of the Invention
The invention generally relates to the field of electronic circuits. Specifically, the invention relates to a low-power electronic circuit system incorporating a real time clock circuit and an electronic switch circuit whereby power requirements for system devices are optimized dependent upon the active or inactive state of the system.
2. Background of the Invention
Numerous electronic applications incorporate the use of real time clock (RTC) circuitry in cooperation with other electronics such as mobile telephones, GPS, personal digital assistants and other portable battery-powered devices.
In these and other systems, an RTC may be used to keep time (seconds, minutes, hours, days, months and years) and can be implemented to enable or “wake up” one or more system components, referred to herein as “main devices”, at user-defined time intervals. Common components in these systems may comprise microprocessors, universal serial bus interface devices, memory devices or RF transmitter/receivers.
In portable applications where a battery power source is used, overall system power consumption is a prime concern. In order to reduce overall power consumption of the system, one or more of the system components is typically put into an inactive or suspended state, sometimes referred to as a standby mode. While this measurably reduces current consumption, there nonetheless remains some standby current used by the devices while in an inactive state. A greater reduction in current while in the inactive state can be achieved by depriving power-controlled devices of supply power as opposed to logically disabling them.
Aside from being a source of a limited power, battery power sources also maintain the undesirable attribute of having a variable voltage across the battery, which variance can be, in the case of a 3.6 V Li-Ion battery, in the range of 17% (3.0 V-4.2V). While an RTC is capable of using a battery supply voltage with this degree of variability, the above-mentioned system components typically cannot and will require the use of a supply voltage ranging not more than 5% from nominal. This has the undesirable result of incompatible supply voltage requirements for the RTC and other system components.
In prior art applications, a voltage regulator circuit can be used to regulate a variable battery supply voltage whereby a relatively stable output voltage from the voltage regulator circuit is used to supply power to the system components with tighter voltage supply requirements. In this instance, the voltage at the voltage regulator output will be lower than the lowest battery voltage, less the required voltage drop across the voltage regulator circuit.
What is needed is a device that can address the above design concerns that is simple in design and low in cost.